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Subject[Patch v4 17/22] CIFS: SMBD: Implement RDMA memory registration
Date
From: Long Li <longli@microsoft.com>

Memory registration is used for transferring payload via RDMA read or write.
After I/O is done, memory registrations are recovered and reused. This
process can be time consuming and is done in a work queue.

Signed-off-by: Long Li <longli@microsoft.com>
---
fs/cifs/smbdirect.c | 428 ++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/cifs/smbdirect.h | 55 +++++++
2 files changed, 483 insertions(+)

diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index 90e2c94..3f2de48 100644
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -49,6 +49,9 @@ static int smbd_post_send_page(struct smbd_connection *info,
struct page *page, unsigned long offset,
size_t size, int remaining_data_length);

+static void destroy_mr_list(struct smbd_connection *info);
+static int allocate_mr_list(struct smbd_connection *info);
+
/* SMBD version number */
#define SMBD_V1 0x0100

@@ -219,6 +222,12 @@ static void smbd_destroy_rdma_work(struct work_struct *work)
wait_event(info->wait_send_payload_pending,
atomic_read(&info->send_payload_pending) == 0);

+ log_rdma_event(INFO, "freeing mr list\n");
+ wake_up_interruptible_all(&info->wait_mr);
+ wait_event(info->wait_for_mr_cleanup,
+ atomic_read(&info->mr_used_count) == 0);
+ destroy_mr_list(info);
+
/* It's not posssible for upper layer to get to reassembly */
log_rdma_event(INFO, "drain the reassembly queue\n");
do {
@@ -475,6 +484,16 @@ static bool process_negotiation_response(
}
info->max_fragmented_send_size =
le32_to_cpu(packet->max_fragmented_size);
+ info->rdma_readwrite_threshold =
+ rdma_readwrite_threshold > info->max_fragmented_send_size ?
+ info->max_fragmented_send_size :
+ rdma_readwrite_threshold;
+
+
+ info->max_readwrite_size = min_t(u32,
+ le32_to_cpu(packet->max_readwrite_size),
+ info->max_frmr_depth * PAGE_SIZE);
+ info->max_frmr_depth = info->max_readwrite_size / PAGE_SIZE;

return true;
}
@@ -773,6 +792,12 @@ static int smbd_ia_open(
rc = -EPROTONOSUPPORT;
goto out2;
}
+ info->max_frmr_depth = min_t(int,
+ smbd_max_frmr_depth,
+ info->id->device->attrs.max_fast_reg_page_list_len);
+ info->mr_type = IB_MR_TYPE_MEM_REG;
+ if (info->id->device->attrs.device_cap_flags & IB_DEVICE_SG_GAPS_REG)
+ info->mr_type = IB_MR_TYPE_SG_GAPS;

info->pd = ib_alloc_pd(info->id->device, 0);
if (IS_ERR(info->pd)) {
@@ -1610,6 +1635,8 @@ struct smbd_connection *_smbd_get_connection(
struct rdma_conn_param conn_param;
struct ib_qp_init_attr qp_attr;
struct sockaddr_in *addr_in = (struct sockaddr_in *) dstaddr;
+ struct ib_port_immutable port_immutable;
+ u32 ird_ord_hdr[2];

info = kzalloc(sizeof(struct smbd_connection), GFP_KERNEL);
if (!info)
@@ -1698,6 +1725,28 @@ struct smbd_connection *_smbd_get_connection(
memset(&conn_param, 0, sizeof(conn_param));
conn_param.initiator_depth = 0;

+ conn_param.responder_resources =
+ info->id->device->attrs.max_qp_rd_atom
+ < SMBD_CM_RESPONDER_RESOURCES ?
+ info->id->device->attrs.max_qp_rd_atom :
+ SMBD_CM_RESPONDER_RESOURCES;
+ info->responder_resources = conn_param.responder_resources;
+ log_rdma_mr(INFO, "responder_resources=%d\n",
+ info->responder_resources);
+
+ /* Need to send IRD/ORD in private data for iWARP */
+ info->id->device->get_port_immutable(
+ info->id->device, info->id->port_num, &port_immutable);
+ if (port_immutable.core_cap_flags & RDMA_CORE_PORT_IWARP) {
+ ird_ord_hdr[0] = info->responder_resources;
+ ird_ord_hdr[1] = 1;
+ conn_param.private_data = ird_ord_hdr;
+ conn_param.private_data_len = sizeof(ird_ord_hdr);
+ } else {
+ conn_param.private_data = NULL;
+ conn_param.private_data_len = 0;
+ }
+
conn_param.retry_count = SMBD_CM_RETRY;
conn_param.rnr_retry_count = SMBD_CM_RNR_RETRY;
conn_param.flow_control = 0;
@@ -1762,8 +1811,19 @@ struct smbd_connection *_smbd_get_connection(
goto negotiation_failed;
}

+ rc = allocate_mr_list(info);
+ if (rc) {
+ log_rdma_mr(ERR, "memory registration allocation failed\n");
+ goto allocate_mr_failed;
+ }
+
return info;

+allocate_mr_failed:
+ /* At this point, need to a full transport shutdown */
+ smbd_destroy(info);
+ return NULL;
+
negotiation_failed:
cancel_delayed_work_sync(&info->idle_timer_work);
destroy_caches_and_workqueue(info);
@@ -2221,3 +2281,371 @@ int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst)

return rc;
}
+
+static void register_mr_done(struct ib_cq *cq, struct ib_wc *wc)
+{
+ struct smbd_mr *mr;
+ struct ib_cqe *cqe;
+
+ if (wc->status) {
+ log_rdma_mr(ERR, "status=%d\n", wc->status);
+ cqe = wc->wr_cqe;
+ mr = container_of(cqe, struct smbd_mr, cqe);
+ smbd_disconnect_rdma_connection(mr->conn);
+ }
+}
+
+/*
+ * The work queue function that recovers MRs
+ * We need to call ib_dereg_mr() and ib_alloc_mr() before this MR can be used
+ * again. Both calls are slow, so finish them in a workqueue. This will not
+ * block I/O path.
+ * There is one workqueue that recovers MRs, there is no need to lock as the
+ * I/O requests calling smbd_register_mr will never update the links in the
+ * mr_list.
+ */
+static void smbd_mr_recovery_work(struct work_struct *work)
+{
+ struct smbd_connection *info =
+ container_of(work, struct smbd_connection, mr_recovery_work);
+ struct smbd_mr *smbdirect_mr;
+ int rc;
+
+ list_for_each_entry(smbdirect_mr, &info->mr_list, list) {
+ if (smbdirect_mr->state == MR_INVALIDATED ||
+ smbdirect_mr->state == MR_ERROR) {
+
+ if (smbdirect_mr->state == MR_INVALIDATED) {
+ ib_dma_unmap_sg(
+ info->id->device, smbdirect_mr->sgl,
+ smbdirect_mr->sgl_count,
+ smbdirect_mr->dir);
+ smbdirect_mr->state = MR_READY;
+ } else if (smbdirect_mr->state == MR_ERROR) {
+
+ /* recover this MR entry */
+ rc = ib_dereg_mr(smbdirect_mr->mr);
+ if (rc) {
+ log_rdma_mr(ERR,
+ "ib_dereg_mr faield rc=%x\n",
+ rc);
+ smbd_disconnect_rdma_connection(info);
+ }
+
+ smbdirect_mr->mr = ib_alloc_mr(
+ info->pd, info->mr_type,
+ info->max_frmr_depth);
+ if (IS_ERR(smbdirect_mr->mr)) {
+ log_rdma_mr(ERR,
+ "ib_alloc_mr failed mr_type=%x "
+ "max_frmr_depth=%x\n",
+ info->mr_type,
+ info->max_frmr_depth);
+ smbd_disconnect_rdma_connection(info);
+ }
+
+ smbdirect_mr->state = MR_READY;
+ }
+ /* smbdirect_mr->state is updated by this function
+ * and is read and updated by I/O issuing CPUs trying
+ * to get a MR, the call to atomic_inc_return
+ * implicates a memory barrier and guarantees this
+ * value is updated before waking up any calls to
+ * get_mr() from the I/O issuing CPUs
+ */
+ if (atomic_inc_return(&info->mr_ready_count) == 1)
+ wake_up_interruptible(&info->wait_mr);
+ }
+ }
+}
+
+static void destroy_mr_list(struct smbd_connection *info)
+{
+ struct smbd_mr *mr, *tmp;
+
+ cancel_work_sync(&info->mr_recovery_work);
+ list_for_each_entry_safe(mr, tmp, &info->mr_list, list) {
+ if (mr->state == MR_INVALIDATED)
+ ib_dma_unmap_sg(info->id->device, mr->sgl,
+ mr->sgl_count, mr->dir);
+ ib_dereg_mr(mr->mr);
+ kfree(mr->sgl);
+ kfree(mr);
+ }
+}
+
+/*
+ * Allocate MRs used for RDMA read/write
+ * The number of MRs will not exceed hardware capability in responder_resources
+ * All MRs are kept in mr_list. The MR can be recovered after it's used
+ * Recovery is done in smbd_mr_recovery_work. The content of list entry changes
+ * as MRs are used and recovered for I/O, but the list links will not change
+ */
+static int allocate_mr_list(struct smbd_connection *info)
+{
+ int i;
+ struct smbd_mr *smbdirect_mr, *tmp;
+
+ INIT_LIST_HEAD(&info->mr_list);
+ init_waitqueue_head(&info->wait_mr);
+ spin_lock_init(&info->mr_list_lock);
+ atomic_set(&info->mr_ready_count, 0);
+ atomic_set(&info->mr_used_count, 0);
+ init_waitqueue_head(&info->wait_for_mr_cleanup);
+ /* Allocate more MRs (2x) than hardware responder_resources */
+ for (i = 0; i < info->responder_resources * 2; i++) {
+ smbdirect_mr = kzalloc(sizeof(*smbdirect_mr), GFP_KERNEL);
+ if (!smbdirect_mr)
+ goto out;
+ smbdirect_mr->mr = ib_alloc_mr(info->pd, info->mr_type,
+ info->max_frmr_depth);
+ if (IS_ERR(smbdirect_mr->mr)) {
+ log_rdma_mr(ERR, "ib_alloc_mr failed mr_type=%x "
+ "max_frmr_depth=%x\n",
+ info->mr_type, info->max_frmr_depth);
+ goto out;
+ }
+ smbdirect_mr->sgl = kcalloc(
+ info->max_frmr_depth,
+ sizeof(struct scatterlist),
+ GFP_KERNEL);
+ if (!smbdirect_mr->sgl) {
+ log_rdma_mr(ERR, "failed to allocate sgl\n");
+ ib_dereg_mr(smbdirect_mr->mr);
+ goto out;
+ }
+ smbdirect_mr->state = MR_READY;
+ smbdirect_mr->conn = info;
+
+ list_add_tail(&smbdirect_mr->list, &info->mr_list);
+ atomic_inc(&info->mr_ready_count);
+ }
+ INIT_WORK(&info->mr_recovery_work, smbd_mr_recovery_work);
+ return 0;
+
+out:
+ kfree(smbdirect_mr);
+
+ list_for_each_entry_safe(smbdirect_mr, tmp, &info->mr_list, list) {
+ ib_dereg_mr(smbdirect_mr->mr);
+ kfree(smbdirect_mr->sgl);
+ kfree(smbdirect_mr);
+ }
+ return -ENOMEM;
+}
+
+/*
+ * Get a MR from mr_list. This function waits until there is at least one
+ * MR available in the list. It may access the list while the
+ * smbd_mr_recovery_work is recovering the MR list. This doesn't need a lock
+ * as they never modify the same places. However, there may be several CPUs
+ * issueing I/O trying to get MR at the same time, mr_list_lock is used to
+ * protect this situation.
+ */
+static struct smbd_mr *get_mr(struct smbd_connection *info)
+{
+ struct smbd_mr *ret;
+ int rc;
+again:
+ rc = wait_event_interruptible(info->wait_mr,
+ atomic_read(&info->mr_ready_count) ||
+ info->transport_status != SMBD_CONNECTED);
+ if (rc) {
+ log_rdma_mr(ERR, "wait_event_interruptible rc=%x\n", rc);
+ return NULL;
+ }
+
+ if (info->transport_status != SMBD_CONNECTED) {
+ log_rdma_mr(ERR, "info->transport_status=%x\n",
+ info->transport_status);
+ return NULL;
+ }
+
+ spin_lock(&info->mr_list_lock);
+ list_for_each_entry(ret, &info->mr_list, list) {
+ if (ret->state == MR_READY) {
+ ret->state = MR_REGISTERED;
+ spin_unlock(&info->mr_list_lock);
+ atomic_dec(&info->mr_ready_count);
+ atomic_inc(&info->mr_used_count);
+ return ret;
+ }
+ }
+
+ spin_unlock(&info->mr_list_lock);
+ /*
+ * It is possible that we can get a MR because other processes may try
+ * to acquire a MR at the same time. If this is the case, retry it.
+ */
+ goto again;
+}
+
+/*
+ * Register memory for RDMA read/write
+ * pages[]: the list of pages to register memory with
+ * num_pages: the number of pages to register
+ * tailsz: if non-zero, the bytes to register in the last page
+ * writing: true if this is a RDMA write (SMB read), false for RDMA read
+ * need_invalidate: true if this MR needs to be locally invalidated after I/O
+ * return value: the MR registered, NULL if failed.
+ */
+struct smbd_mr *smbd_register_mr(
+ struct smbd_connection *info, struct page *pages[], int num_pages,
+ int tailsz, bool writing, bool need_invalidate)
+{
+ struct smbd_mr *smbdirect_mr;
+ int rc, i;
+ enum dma_data_direction dir;
+ struct ib_reg_wr *reg_wr;
+ struct ib_send_wr *bad_wr;
+ unsigned long long t1 = rdtsc();
+
+ if (num_pages > info->max_frmr_depth) {
+ log_rdma_mr(ERR, "num_pages=%d max_frmr_depth=%d\n",
+ num_pages, info->max_frmr_depth);
+ return NULL;
+ }
+
+ smbdirect_mr = get_mr(info);
+ if (!smbdirect_mr) {
+ log_rdma_mr(ERR, "get_mr returning NULL\n");
+ return NULL;
+ }
+ smbdirect_mr->need_invalidate = need_invalidate;
+ smbdirect_mr->sgl_count = num_pages;
+ sg_init_table(smbdirect_mr->sgl, num_pages);
+
+ for (i = 0; i < num_pages - 1; i++)
+ sg_set_page(&smbdirect_mr->sgl[i], pages[i], PAGE_SIZE, 0);
+
+ sg_set_page(&smbdirect_mr->sgl[i], pages[i],
+ tailsz ? tailsz : PAGE_SIZE, 0);
+
+ dir = writing ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+ smbdirect_mr->dir = dir;
+ rc = ib_dma_map_sg(info->id->device, smbdirect_mr->sgl, num_pages, dir);
+ if (!rc) {
+ log_rdma_mr(INFO, "ib_dma_map_sg num_pages=%x dir=%x rc=%x\n",
+ num_pages, dir, rc);
+ goto dma_map_error;
+ }
+
+ rc = ib_map_mr_sg(smbdirect_mr->mr, smbdirect_mr->sgl, num_pages,
+ NULL, PAGE_SIZE);
+ if (rc != num_pages) {
+ log_rdma_mr(INFO,
+ "ib_map_mr_sg failed rc = %x num_pages = %x\n",
+ rc, num_pages);
+ goto map_mr_error;
+ }
+
+ ib_update_fast_reg_key(smbdirect_mr->mr,
+ ib_inc_rkey(smbdirect_mr->mr->rkey));
+ reg_wr = &smbdirect_mr->wr;
+ reg_wr->wr.opcode = IB_WR_REG_MR;
+ smbdirect_mr->cqe.done = register_mr_done;
+ reg_wr->wr.wr_cqe = &smbdirect_mr->cqe;
+ reg_wr->wr.num_sge = 0;
+ reg_wr->wr.send_flags = IB_SEND_SIGNALED;
+ reg_wr->mr = smbdirect_mr->mr;
+ reg_wr->key = smbdirect_mr->mr->rkey;
+ reg_wr->access = writing ?
+ IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE :
+ IB_ACCESS_REMOTE_READ;
+
+ /*
+ * There is no need for waiting for complemtion on ib_post_send
+ * on IB_WR_REG_MR. Hardware enforces a barrier and order of execution
+ * on the next ib_post_send when we actaully send I/O to remote peer
+ */
+ rc = ib_post_send(info->id->qp, &reg_wr->wr, &bad_wr);
+ if (!rc) {
+ profiling_add_histogram(
+ rdtsc()-t1, info->smbd_register_mr_cycles);
+ return smbdirect_mr;
+ }
+
+ log_rdma_mr(ERR, "ib_post_send failed rc=%x reg_wr->key=%x\n",
+ rc, reg_wr->key);
+
+ /* If all failed, attempt to recover this MR by setting it MR_ERROR*/
+map_mr_error:
+ ib_dma_unmap_sg(info->id->device, smbdirect_mr->sgl,
+ smbdirect_mr->sgl_count, smbdirect_mr->dir);
+
+dma_map_error:
+ smbdirect_mr->state = MR_ERROR;
+ if (atomic_dec_and_test(&info->mr_used_count))
+ wake_up(&info->wait_for_mr_cleanup);
+
+ return NULL;
+}
+
+static void local_inv_done(struct ib_cq *cq, struct ib_wc *wc)
+{
+ struct smbd_mr *smbdirect_mr;
+ struct ib_cqe *cqe;
+
+ cqe = wc->wr_cqe;
+ smbdirect_mr = container_of(cqe, struct smbd_mr, cqe);
+ smbdirect_mr->state = MR_INVALIDATED;
+ if (wc->status != IB_WC_SUCCESS) {
+ log_rdma_mr(ERR, "invalidate failed status=%x\n", wc->status);
+ smbdirect_mr->state = MR_ERROR;
+ }
+ complete(&smbdirect_mr->invalidate_done);
+}
+
+/*
+ * Deregister a MR after I/O is done
+ * This function may wait if remote invalidation is not used
+ * and we have to locally invalidate the buffer to prevent data is being
+ * modified by remote peer after upper layer consumes it
+ */
+int smbd_deregister_mr(struct smbd_mr *smbdirect_mr)
+{
+ struct ib_send_wr *wr, *bad_wr;
+ struct smbd_connection *info = smbdirect_mr->conn;
+ int rc = 0;
+ unsigned long long t1 = rdtsc();
+
+ if (smbdirect_mr->need_invalidate) {
+ /* Need to finish local invalidation before returning */
+ wr = &smbdirect_mr->inv_wr;
+ wr->opcode = IB_WR_LOCAL_INV;
+ smbdirect_mr->cqe.done = local_inv_done;
+ wr->wr_cqe = &smbdirect_mr->cqe;
+ wr->num_sge = 0;
+ wr->ex.invalidate_rkey = smbdirect_mr->mr->rkey;
+ wr->send_flags = IB_SEND_SIGNALED;
+
+ init_completion(&smbdirect_mr->invalidate_done);
+ rc = ib_post_send(info->id->qp, wr, &bad_wr);
+ if (rc) {
+ log_rdma_mr(ERR, "ib_post_send failed rc=%x\n", rc);
+ smbd_disconnect_rdma_connection(info);
+ goto done;
+ }
+ wait_for_completion(&smbdirect_mr->invalidate_done);
+ smbdirect_mr->need_invalidate = false;
+ } else
+ /*
+ * For remote invalidation, just set it to MR_INVALIDATED
+ * and defer to mr_recovery_work to recover the MR for next use
+ */
+ smbdirect_mr->state = MR_INVALIDATED;
+
+ /*
+ * Schedule the work to do MR recovery for future I/Os
+ * MR recovery is slow and we don't want it to block the current I/O
+ */
+ queue_work(info->workqueue, &info->mr_recovery_work);
+
+ profiling_add_histogram(rdtsc()-t1, info->smbd_deregister_mr_cycles);
+
+done:
+ if (atomic_dec_and_test(&info->mr_used_count))
+ wake_up(&info->wait_for_mr_cleanup);
+
+ return rc;
+}
diff --git a/fs/cifs/smbdirect.h b/fs/cifs/smbdirect.h
index e9bd938..b8ddfe9 100644
--- a/fs/cifs/smbdirect.h
+++ b/fs/cifs/smbdirect.h
@@ -87,6 +87,29 @@ struct smbd_connection {
int receive_credit_target;
int fragment_reassembly_remaining;

+ /* Memory registrations */
+ /* Maximum number of RDMA read/write outstanding on this connection */
+ int responder_resources;
+ /* Maximum number of SGEs in a RDMA write/read */
+ int max_frmr_depth;
+ /*
+ * If payload is less than or equal to the threshold,
+ * use RDMA send/recv to send upper layer I/O.
+ * If payload is more than the threshold,
+ * use RDMA read/write through memory registration for I/O.
+ */
+ int rdma_readwrite_threshold;
+ enum ib_mr_type mr_type;
+ struct list_head mr_list;
+ spinlock_t mr_list_lock;
+ /* The number of available MRs ready for memory registration */
+ atomic_t mr_ready_count;
+ atomic_t mr_used_count;
+ wait_queue_head_t wait_mr;
+ struct work_struct mr_recovery_work;
+ /* Used by transport to wait until all MRs are returned */
+ wait_queue_head_t wait_for_mr_cleanup;
+
/* Activity accoutning */
/* Pending reqeusts issued from upper layer */
int smbd_send_pending;
@@ -157,6 +180,8 @@ struct smbd_connection {
unsigned int count_send_empty;

#define SIZE_LONG_LONG 64
+ unsigned long long smbd_register_mr_cycles[SIZE_LONG_LONG];
+ unsigned long long smbd_deregister_mr_cycles[SIZE_LONG_LONG];
unsigned long long smbd_write_cycles[SIZE_LONG_LONG];
unsigned long long smbd_recv_cycles[SIZE_LONG_LONG];
unsigned long long recv_done_cycles[SIZE_LONG_LONG];
@@ -265,6 +290,36 @@ void smbd_destroy(struct smbd_connection *info);
int smbd_recv(struct smbd_connection *info, struct msghdr *msg);
int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst);

+enum mr_state {
+ MR_READY,
+ MR_REGISTERED,
+ MR_INVALIDATED,
+ MR_ERROR
+};
+
+struct smbd_mr {
+ struct smbd_connection *conn;
+ struct list_head list;
+ enum mr_state state;
+ struct ib_mr *mr;
+ struct scatterlist *sgl;
+ int sgl_count;
+ enum dma_data_direction dir;
+ union {
+ struct ib_reg_wr wr;
+ struct ib_send_wr inv_wr;
+ };
+ struct ib_cqe cqe;
+ bool need_invalidate;
+ struct completion invalidate_done;
+};
+
+/* Interfaces to register and deregister MR for RDMA read/write */
+struct smbd_mr *smbd_register_mr(
+ struct smbd_connection *info, struct page *pages[], int num_pages,
+ int tailsz, bool writing, bool need_invalidate);
+int smbd_deregister_mr(struct smbd_mr *mr);
+
void profiling_display_histogram(
struct seq_file *m, unsigned long long array[]);
#endif
--
2.7.4
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